A telescoped Ru(II)/Fe-catalyzed strategy enabling direct access to highly substituted indenones from simple aromatic ketones is reported. The sequence merges Ru(II)-catalyzed ketone-directed ortho-C-H alkenylation with FeCl3-mediated formal 2 + 2 cycloaddition/ring-opening cascade, delivering diverse indenone derivatives in good to excellent yields with broad functional group tolerance. Mechanistic studies support the formation of an ortho-keto-cinnamate that undergoes Lewis acid-promoted enolate formation, cyclization, and rearomatization. This step and atom-economical protocol offer a practical alternative to conventional indenone syntheses and a versatile platform for late-stage functionalization.
Bhat et al. (Mon,) studied this question.